1. Field of the Invention
The present invention relates generally to a wired, non-intrusive remote control device and to a method for interfacing the remote control device.
2. Description of the Prior Art
In many present-day computer applications it is desirable to interconnect the computer to a variety of peripheral units. These units may include printers, terminals, digital storage units and even remote control devices. In addition, it may also be desirable to interconnect two or more computers in a network arrangement, either in one location or in remote locations.
In order to effect communication between the computer and the peripheral units, and/or between networked computers, the communicating device must convert its internal electronic signals into a set of electronic signals which can be properly received and processed by the computer. One industry standard set of electronic signals which has been established for communications between various devices is known as "RS232" standard interface signals, in which a digital "0" and "1" are represented by plus or minus twelve volt signals, respectively.
In order to operate with RS232 signal levels, a computer must have its own interface circuitry to convert the RS232 voltage levels into the internal voltage levels actually used in the machine. In many computers, a special RS232 serial communications interface or "port" is provided for communication with external units. Each such port includes a number of lines or conductors.
A problem that has arisen with many computers is that there are usually not enough ports available to accommodate simultaneous interconnection of all necessary external units. This problem is particularly noteworthy with automotive engine analyzers. Engine analyzers are essentially special-purpose computer systems which communicate with a number of peripheral devices, such as gas analyzers, printers, and the like, via conventional RS232 serial communications ports. Each peripheral device is assigned to a dedicated, single-device port for communication with the engine analyzer. Some devices, like printers, use most if not all of the available RS232 port lines to effect data communication. Others, like gas analyzers, use only a few of the available RS232 port lines, with the remaining lines going unused.
Under engine analyzer control, gas analyzers are used to diagnose the exhaust gases of a motor vehicle, including collecting and measuring concentration levels of certain ingredients of exhaust gases. Typically, the gas analyzer test involves having an automotive technician subject the vehicle under test to varying driving conditions. This requires the technician to be seated in the driver's seat of the running vehicle so that the vehicle speed (MPH) may be appropriately varied during the test. Presently, in order to properly start or abort the test, the seated technician must have an assistant standing next to the engine analyzer entering the appropriate keyboard commands (i.e., `start` test, `abort` test). This is because the technician is necessarily a considerable distance from the engine analyzer and particularly the analyzer's command-entering keyboard. The technician is then guided by a drive trace on the analyzer display which assists him in maintaining the vehicle within a varying range of speeds. The present inventors have recognized that by interfacing a wired remote control device to the engine analyzer, appropriate test initiation and related commands can be remotely communicated by the technician to the engine analyzer, obviating the need for an assistant.
However, because the maximum number of available serial RS232 ports are predetermined by the system architecture of the engine analyzer, adding even one extra port to accommodate communication with a remote control device, the only function of which would be to remotely start or abort the emissions test described above, is generally not practical. It is possible to use non-wired remote control units which communicate by radio or light waves with the engine analyzer, however this also requires modification of the engine analyzer.